First, I believe we have almost nothing to go off of so speculation based off the lore is the only preliminary guessing that can be done. Unless I have missed an announcement or a key hint from the developers, we may proceed.
We should at once consider the very nature of these beings, these Aurora Specters. Then we can gather a greater understanding of their supposed role in the upcoming content. The Specters are in some way related to Uras-Beherit. They exist outside of our space-time and could be some of the oldest beings to exist in our universe besides Uras-Beherit, who could have created them. This also means that they could have been created in the pre-universe where Uras-Beherit did nothing as far as we know. Whatever the case may be we do know that the Aurora Specters were imprisoned by someone or something for a crime or because of the threat they pose. When this occurred is a very interesting question and will probably be a sub-plot within Shamash's story and his origins.
The nature of Uras-Beherit is one of pure concentrated malice. But, it is less than that and is all the more terrible for this. It is nothing. It is naught. Uras-Beherit is older than light and older than the universe. Suffering is the only goal, but it isn't even the goal. Uras-Beherit is suffering. Beyond the emotion of suffering. Beyond our very definition of it; there is Uras-Beherit. The Aurora Specters are linked in this way as well. They are "daemonic entities whose eldritch powers are only rivaled by their thirst for the Raiders’ blood" which is very close to what Uras is all about.
Uras-Beherit is characterized by your interpretation of "him" when you play as an antagonist. In these dialogues we see that he greatly loathes the Raiders, the Protectors and Locals in general. But, why? Because they wish to dominate the Aleph in such a way that it will no longer cause the suffering he embodies. The humans never understood the meaning and purpose of Aleph. They have inadvertently given themselves away wholesale to the miraculous substance, an act which we all know ends in disaster. Because they are not dominating the Aleph, or their actions are not leading to domination of the Aleph. Uras considers them allies and his influence within the Flow of Aleph is so strong that humans, who willfully consume Aleph, cannot perceive the antagonist as the misshapen Raider they truly are. The Aurora Specters do not appear, from the Roadmap picture, to have any sort of traits from the Raiders such as eyes or skin. This shows that their ties with Uras-Beherit might simply begin and end with their occupation of the same non-space-time. Uras-Beherit, after all, cannot be anything we are not ourselves.
Now, you could make the argument that Aurora Specters are the more advanced Apprentices who we see in Enemy Within. But, it seems much more likely that the Apprentices are simply more Uras-Beherit, more suffering embodied, which were made to take the form of very strong warriors so that they may cause more suffering and thus more Uras. Whereas the Aurora Specters are in a class all their own. They are not more Uras-Beherit and do not serve him in the same capacity as the Apprentices. Probably more akin to how the Raiders serve Harec. They do what he says because he is determined, cunning and very intelligent but also because they have something to gain from helping him in his quest.
Finally, their prison. Which is opened, on accident, by Shamash. Uras-Beherit either had no idea the Aurora Specters could be freed in such a way, I don't see how considering Uras is older than knowledge itself, or he did know the Aurora Specters could be freed in such a way but was prevented in freeing them while stuck inside Ku'ur Sag.
Uras-Beherit does nothing to stop Shamash's return, which Uras would know was going to happen, did know it was going to happen and will know it is going to happen. You see, Uras-Beherit is what you find when you go deep into the Aleph flow. It appears to stem straight from his nothingness. The nature of the Aleph flow is one where all time and space are meaningless and blend together like a river. A river wider than infinity and deeper than eternity. Because of this we may postulate that Uras perceives time all at once and thus can be in all times at once. Which means he knew about Shamash and many other things that have happened since then and before. All of it. Except...
Weavers. Iune is a Weaver and their order is older than the breaking of the planet. Weavers learn to attune themselves to the Aleph flow and with it can communicate with others inside the Aleph flow, those dead for centuries and those yet born. Here is the only place a unified assault on Uras-Beherit could have taken place, as they are outside the bounds of space-time and no longer can be perceived with any foresight outside of the non-moment they occupy. In this way the Locals were able to seal Uras away and likely the Aurora Specters with him. This could have happened thousands of years before the breaking of the planet. Or thousands of years after the events of the game. Or thousands of times right now. Such is the nature of non-space-time, of the Aleph flow.
Uras-Beherit does not like females, his silly remarks aside. They give him pause in his actions and it is known that the Nuns Custodia, all females, at least were stewards to the Protectors in some fashion. This purpose has been lost to time but the traditions carried on. They were likely a strong force that dealt with Uras-Beherit or whichever incarnation he was at the time and it is also possible they did battle with the Aurora Specters at some point.
To sum it all up; Aurora Specters are likely powerful individuals with a less than direct connection with Uras-Beherit. They possibly have a lot of history with Shae's and Iune's ancestry. They do not like Locals, especially ones who have dominated the Aleph, and thus have no allegiance to Shamash who has clearly dominated the Aleph expertly. They will aid the antagonist but it is likely they have ulterior motives of which Uras may or may not be aware of considering their dubious entry. Their hatred of the Raiders could be Uras' influence or simply the need to eliminate a great threat to their existence.
I dunno, what do you think?
